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	<div id="winchm_template_button"><A href="x64_architecture.htm" title="Previous topic"><img id="winchm_template_prev" alt="Previous topic" src="../template2/btn_prev_n.gif" border="0"></a><A href="annotated_x64_disassembly.htm" title="Next topic"><img id="winchm_template_next" alt="Next topic" src="../template2/btn_next_n.gif" border="0"></a></div>
	<div id="winchm_template_navigation">Help &gt; 
<A href="introduction6.htm">Debugging Tools for Windows (WinDbg, KD, CDB, NTSD)</A> &gt; <A href="debugging_resources.htm">Debugging Resources</A> &gt; <A href="processor_architecture.htm">Processor Architecture</A> &gt; <A href="the_x64_processor.htm">The x64 Processor</A> &gt; </div>
	<div id="winchm_template_title">x64 Instructions</div>
</div>
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	<div id="winchm_template_content"><div id="mainSection"><p>Most x86 instructions continue to be valid for x64 in 64-bit mode.  Some rarely-used operations are no longer supported in 64-bit mode, such as:</p>
<ul>
<li>
<p>binary-coded decimal arithmetic instructions: AAA, AAD, AAM, AAS, DAA, DAS</p>
</li>
<li>
<p>BOUND</p>
</li>
<li>
<p>PUSHAD and POPAD</p>
</li>
<li>
<p>most operations that dealt with segment registers, such as PUSH DS and POP DS.  (Operations that use the FS or GS segment registers are still valid.)</p>
</li>
</ul>
<p>The x64 instruction set includes recent additions to the x86, such as SSE 2.  Programs compiled for x64 can freely use these instructions.</p>
<h3><a id="Data_Transfer"></a><a id="data_transfer"></a><a id="DATA_TRANSFER"></a>Data Transfer</h3>
<p>The x64 provides new variants of the MOV instruction that can handle 64-bit immediate constants or memory addresses.</p>
<table>
<tr>
<td>
<p>MOV</p>
</td>
<td>
<p><b>r</b>,#n</p>
</td>
<td>
<p><b>r</b> = #n</p>
</td>
</tr>
<tr>
<td>
<p>MOV</p>
</td>
<td>
<p><b>rax</b>, m</p>
</td>
<td>
<p>Move contents at 64-bit address to <b>rax</b>.</p>
</td>
</tr>
<tr>
<td>
<p>MOV</p>
</td>
<td>
<p>m, <b>rax</b></p>
</td>
<td>
<p>Move contents of <b>rax</b> to 64-bit address.</p>
</td>
</tr>
</table>
<p> </p>
<p>The x64 also provides a new instruction to sign-extend 32-bit operands to 64 bits.</p>
<table>
<tr>
<td>
<p>MOVSXD</p>
</td>
<td>
<p><b>r1</b>, <b>r</b>/m</p>
</td>
<td>
<p>Move DWORD with sign extension to QWORD.</p>
</td>
</tr>
</table>
<p> </p>
<p>Ordinary MOV operations into 32-bit subregisters automatically zero extend to 64 bits, so there is no MOVZXD instruction.</p>
<p>Two SSE instructions can be used to move 128-bit values (such as GUIDs) from memory to an <b>xmm</b><i>n</i> register or vice versa.</p>
<table>
<tr>
<td>
<p>MOVDQA</p>
</td>
<td>
<p><b>r1</b>/m, <b>r2</b>/m</p>
</td>
<td>
<p>Move 128-bit aligned value to <b>xmm</b><i>n</i> register, or vice versa.</p>
</td>
</tr>
<tr>
<td>
<p>MOVDQU</p>
</td>
<td>
<p><b>r1</b>/m, <b>r2</b>/m</p>
</td>
<td>
<p>Move 128-bit value (not necessarily aligned) to register, or vice versa.</p>
</td>
</tr>
</table>
<p> </p>
<h3><a id="Data_Conversion"></a><a id="data_conversion"></a><a id="DATA_CONVERSION"></a>Data Conversion</h3>
<table>
<tr>
<td>
<p>CDQE</p>
</td>
<td>
<p>Convert dword (<b>eax</b>) to qword (<b>rax</b>).</p>
</td>
</tr>
<tr>
<td>
<p>CQO</p>
</td>
<td>
<p>convert qword (<b>rax</b>) to oword (<b>rdx</b>:<b>rax</b>).</p>
</td>
</tr>
</table>
<p> </p>
<h3><a id="String_Manipulation"></a><a id="string_manipulation"></a><a id="STRING_MANIPULATION"></a>String Manipulation</h3>
<table>
<tr>
<td>
<p>MOVSQ</p>
</td>
<td>
<p>Move qword from <b>rsi</b> to <b>rdi.</b></p>
</td>
</tr>
<tr>
<td>
<p>CMPSQ</p>
</td>
<td>
<p>Compare qword at <b>rsi</b> with <b>rdi.</b></p>
</td>
</tr>
<tr>
<td>
<p>SCASQ</p>
</td>
<td>
<p>Scan qword at <b>rdi</b>. Compares qword at <b>rdi</b> to <b>rax</b>.</p>
</td>
</tr>
<tr>
<td>
<p>LODSQ</p>
</td>
<td>
<p>Load qword from <b>rsi</b> into <b>rax</b><i>.</i></p>
</td>
</tr>
<tr>
<td>
<p>STOSQ</p>
</td>
<td>
<p>Store qword to <b>rdi</b> from <b>rax</b><i>.</i></p>
</td>
</tr>
</table>
<p> </p></div></div>	
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